Astronomers clarify the Sun’s future and its end

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[EN VIDÉO] Mission Gaia: The Milky Way will soon be mapped
ESA’s Gaia mission has measured the positions and velocities of a billion stars in the Milky Way. This will make it possible to reconstruct the history of our galaxy, to better understand its structure, but also to search for dark matter and exoplanets.

The dazzling post-World War II advances of nuclear astrophysics, complementing the equally rapid constitution in the 1930s of the theory of stellar structure, gave us the life-and-death keys to starsand therefore of course the one that concerns us the most: the Sun.

There are still more unknowns on these topics, and we know that the third phase of the publication of ESA’s Gaia satellite was completed 13 June 2022 will be helpful in this regard. let’s remember that Gaia is an astrometry mission intended to give us more precise determinations of gear and positions in The Milky Way of more than a billion stars.

Gaia must also provide for brightness apparently and color of these stars. Thus, the temperature determining the color of a star according to Vienna’s famous law and the distance to a star being known, one can draw an absolute luminosity from it and more accurately draw a version of the famous diagram of astronomers Danish and American Ejnar Hertzsprung and Henry Norris Russell.

They proposed it independently in the early 1910s, and it was originally a matter of showing how the known stars in the Milky Way were distributed in a diagram giving the luminosity and spectral class of these stars or their absolute size depending on their temperature. We then obtain a distribution in “z” seen in mirror with a transverse band where most of the stars are concentrated and which we call main order (main order English).

The stars in different plenty spend most of their lives on this tape from birth, but then switch places until they leave the main sequence at the end of their lives. A better determination of Hertzsprung-Russell diagram (HR) will therefore affect what we know about the life and death of stars.

A presentation of the first results of Gaia a few years ago. © The European Space AgencyESA

5,863 analogues of the Sun discovered by Gaia

In a recent press release from ESA, the astronomer writes: Orlagh Creevey, who works at the Observatoire de la Côte d’Azur, explains that this is indeed what happened, thanks in particular to the work that she and her colleagues have produced based on the latest data from Gaia. This new diagram contains so much very precise information that astronomers were able to identify fine details that had never been seen before, allowing them to learn more about the Sun’s fate.

For this, Orlagh and his colleagues looked for stars with temperatures, gravity of surface, compositions, masses and radii, all of which are similar to the current Sun. They found 5,863 stars that matched their criteria in the Gaia data. However, since these analogues of the Sun are not all located in the same places on the HR diagram, we can infer that they represent different points on our star’s past and future evolutionary trajectory.

While the mass of the star changes relatively little during its lifetime, the temperature and size of the star varies considerably as it ages, becoming, for example, a red giant, then a white dwarf (white dwarf English). These changes are driven by the type of reactions of nuclear fusion that takes place inside the star, such as the beginning of the fusion of atoms ofheliumand by the localization inside the star of these reactions.

The new statistics thus produced allow us to conclude that the Sun will reach its maximum temperature in a little less than 4 billion years, and that it will become a red giant between one and three billion years later. Earth will have become uninhabitable long before, the evolution of the Sun’s brightness leading to the evaporation of these oceans in about a billion years.

Hertzsprung-Russell diagrams drawn with Gaia data. The evolutionary trajectory of the Sun is shown, inferred from similar stars in the Gaia data. © ESA, Gaia, DPAC, CC by-sa 3.0, IGO

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